docs: async def wait(self):
          """EventSourceResponse object is used for streaming data to the client,
          this method returns future, so we can wain until connection will
          be closed or other task explicitly call ``stop_streaming`` method.
          """
          if self._ping_task is None:
              raise RuntimeError('Response is not started')
          with contextlib.suppress(asyncio.CancelledError):
              await self._ping_task